/Engine/Source/Runtime/Core/Public/Logging/MessageLog.h
Check whether there are any messages present for this log. If the log is paged, this will check if there are any messages on the current page. This call will cause a flush so that the logs state is properly reflected.
The number of messages that pass our filter
int32 NumMessages ( [EMessageSeverity::Type](API\Runtime\Core\Logging\EMessageSeverity__Type) InSeverityFilter )